Abstract

Geophysical granular flows occur at the surface of the Earth and other planets with reduced atmospheric pressure. In this paper, we investigate the run-out of dam-break flows of particle-air mixtures with fine (\(d=75\,\upmu {\hbox {m}}\)) or coarse (\(d=150\,\upmu {\hbox {m}}\)) grains in a flume with different bottom roughness (\(\delta\)) and vacuum degrees (\(P^*\)). Our results reveal an increase of the flow run-out as \(d/\delta\) decreases for fine \(d=75 \,\upmu {\hbox {m}}\)-particles, and run-out decreases with the dimensionless ambient pressure (\(P^*\)) for a given \(d/\delta\). In contrast, the run-out for coarser \(d=150\,\upmu {\hbox {m}}\)-particles, is almost invariant respect to \(P^*\) and \(d/\delta\). These results show that autofluidization of fine-grained flows demonstrated by earlier works at ambient pressure also occurs at reduced pressure though being less efficient. Hence, autofluidization is a mechanism, among others, to explain long run-out of geophysical flows in different environments.

Graphic Abstract

中文翻译：

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底部粗糙度和环境压力条件对实验溃坝颗粒流的位置的影响

摘要

地球物理颗粒流在大气压力降低的情况下发生在地球和其他行星的表面。在本文中，我们研究了具有精细（\（d = 75 \，\ upmu {\ hbox {m}} \））或粗糙（\（d = 150 \，\ upmu {\ hbox {m}} \））槽中的谷粒具有不同的底部粗糙度（\（\ delta \））和真空度（\（P ^ * \））。我们的结果表明，细颗粒（（d = 75 \，\ upmu {\ hbox {m}} \））的\（d / \ delta \）减小时，流量跳动增加，并且随着给定\（d / \ delta \）的无量纲环境压力（\（P ^ * \））。相比之下，跳动会变得更粗\（d = 150 \，\ upmu {\ hbox {m}} \）-粒子对于\（P ^ * \）和\（d / \ delta \）几乎是不变的。这些结果表明，较早的工作在环境压力下表现出的细颗粒流自动流化，尽管效率较低，但在减压下也会发生。因此，自流化是一种机制，用于解释在不同环境中地球物理流的长期耗尽。

图形摘要